Composition and method for preparing chemically-resistant roughened copper surfaces for bonding to substrates

ABSTRACT

The invention is directed to a method and composition for providing chemically-resistant roughened copper surfaces suitable for subsequent multilayer lamination. In one embodiment, a smooth copper surface is contacted with an adhesion promoting composition under conditions effective to provide a roughened copper surface, the adhesion promoting composition comprising an oxidizer, a pH adjuster, a topography modifier, and a sulfur-containing coating stabilizer. In another embodiment, a smooth copper surface is contacted with an adhesion promoting composition under conditions effective to provide a roughened copper surface, the adhesion promoting composition comprising an oxidizer, a pH adjuster, and a topography modifier. Then, in a subsequent step, the roughened copper surface is contacted with an acid resistance promoting composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority benefits fromU.S. patent application Ser. No. 10/782,177 filed Feb. 17, 2004 now U.S.Pat. No. 6,946,027, which is in turn a divisional of and claims prioritybenefits from U.S. patent application Ser. No. 10/143,389 filed May 10,2002, now U.S. Pat. No. 6,716,281. The '389 patent application isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to preparing copper surfaces for bondingto substrates used in the manufacture of printed circuit boards (PCB's).More particularly, the invention relates to the manufacture ofmultilayer PCB's.

BACKGROUND OF THE INVENTION

Multilayer PCB's are constructed by interleaving imaged conductivelayers of copper with dielectric layers to make a multilayer sandwich.The dielectric layers are organic resin layers that bond the copperlayers together. Typically, the layers of copper and dielectric arebonded together by the application of heat and pressure. The surface ofthe copper is smooth, however, and does not bond easily to thedielectric layer.

Improved bonding can be achieved by etching or otherwise roughening thesurface of the copper to provide microscopic crevices and ridges in thesurface of the copper. For example, mechanical means may be used toroughen the copper surface. Unfortunately, delicate circuit patterns aresusceptible to damage if mechanically roughened. Thus, there is a needfor a copper surface roughening process that does not require mechanicalroughening of the copper surface.

Oxide processes are also known in which an oxide having a rough surfaceis formed on the copper surface. The oxide may be formed by chemicaltreatment of the copper. One such oxide process is described in U.S.Pat. No. 4,512,818, which provides a treatment solution for theformation of black oxide layers on copper surfaces of multi-layeredprinted circuits. The treatment solution comprises an oxidant and ahydroxide and is characterized by the addition of a water soluble ordispersible polymer to regulate the properties of the black oxidesolution.

Another oxide process is described in U.S. Pat. No. 5,861,076. The '076patent describes a bond enhancement process for promoting strong, stableadhesive bonds between surfaces of copper foil and adjacent resinimpregnated substrates or superimposed metallic sublayers. According tothe process of the invention, a black oxide-coated copper surface istreated with an aqueous reducing solution containing sodiummetabisulfite and sodium sulfide to convert the black oxide coating to aroughened metallic copper coating. The roughened metallic copper-coatedsurface is then passivated and laminated to a resin impregnatedsubstrate.

U.S. Pat. No. 5,492,595 also pertains to an oxide roughening process.The '595 patent describes a method for treating an oxidized surface of acopper film for bonding to a resinous layer. According to the method ofthe invention, an oxidized surface of a copper film having cupric oxidewhiskers protruding therefrom is contacted with an acidic reducingsolution containing thiosulfate to produce a reduced copper surface. Thereduced copper surface is then rinsed with an acidic solution, andpreferably treated with a passivating agent to minimize any reoxidationprior to laminate formation. A preferred passivating agent is2-mercaptobenzothiazole.

Oxide processes, while well known, have many shortcomings. A typicaloxide process is run at such high temperatures that the substrate isoften distorted, leading to quality control problems and additionalproduction costs. The oxidation process is also associated withuniformity problems in which portions of the copper surface are notoxidized or coated by the oxidizing solution. Uniformity problems leadto partial delamination in the multilayer PCB's. To avoid this problemthe PCB is often run through multiple passes to obtain a more uniformoxide coating. Performing multiple passes adds considerably toproduction cost. Thus, there is a need for a copper roughening processthat does not require multiple passes or high temperature, and that doesnot suffer from the uniformity problems of conventional oxide processes.

Another shortcoming of the typical chemical oxide modification processis that a strong reducing agent, such as dimethylamine borane, isapplied to the oxide coating to obtain an even oxide coating. This typeof adhesion promotion process produces an oxide coating that is fragileand prone to scratching during handling. Inspection of the circuitryprior to lamination is difficult because of the fragility of the oxidecoating. Therefore, there is a need for an adhesion promotion processthat permits a less problematic inspection after the adhesion promotionprocess and prior to the lamination step.

In response to the various problems associated with traditional oxideprocesses, and in particular their time consuming nature and highprocessing temperatures, alternative oxide coating processes have beendeveloped. These alternative processes combine the oxidation function ofthe traditional processes with a controlled etch that actually roughensthe underlying copper surface while oxidizing it at the same time. Thesealternative oxide coating processes tend to be much faster thantraditional oxide processes because they form bonds with increasedstrength and therefore do not require multiple passes. In addition, thealternative methods do not require high temperature processing.

One alternative oxide coating process is described in U.S. Pat. No.5,800,859. The process includes a treating step in which a metal surfaceis contacted with an adhesion promotion material. The adhesion promotionmaterial includes 0.1 to 20% by weight hydrogen peroxide, an inorganicacid, an organic corrosion inhibitor and a surfactant. The surfactant ispreferably a cationic surfactant, usually an amine surfactant and mostpreferably a quaternary ammonium surfactant.

Another alternative oxide coating process is described in U.S. patentapplication Ser. No. 09/479,089, which is incorporated herein byreference in its entirety. The '089 application describes a method andcomposition for providing roughened copper surfaces suitable forsubsequent multilayer lamination. The method involves contacting asmooth copper surface with an adhesion promoting composition whichincludes an oxidizer, a pH adjuster, a topography modifier, and either acoating promoter or a uniformity enhancer.

While alternative oxide processes such as that described the '089application are advantageous over conventional oxide coating processesfor a variety of reasons, the roughened copper surfaces formed by suchprocesses exhibit chemical sensitivity and thus tend to be susceptibleto chemical attack. Chemical attack typically occurs during postlamination processing steps. After a multilayer copper and dielectricsandwich is formed through the lamination process, certain postlamination processing steps are performed to prepare the multilayer PCB.

For example, “through-holes” are drilled through the multilayer sandwichin order to connect the inner layers of the circuit board. The act ofdrilling these holes typically leaves traces of resin smear on thethrough-hole interconnections that must be removed by a desmear process.One desmear process involves the application of a solvent sweller and apermanganate etch which can chemically attack the bond between thecopper surface and dielectric resin at the site of the through holes.The permanganate etch is typically followed by an acid neutralizer whichcan also chemically attack the bond and cause delamination. While otherthrough-hole cleaning techniques are known, such as plasma etch or laserablation, these processes generate intense heat which can also attackthe copper/resin interface.

Once the desmear process is completed, the drilled holes are madeconductive through direct metalization or similar processes. Theseprocesses involve numerous alkaline and acid processing steps, all ofwhich can chemically attack the copper/resin interface. Further, theconductive through-hole is usually sealed with a layer of electrolyticcopper. The electrolytic process involves alkaline and acidic bathswhich can also lead to chemical attack of the through-holeinterconnects. The result of these chemical attacks is the delaminationof the sandwich layers in the area of the through holes.

The chemically attacked area is termed “pink ring” or “wedge void” inthe circuit board industry. The formation of pink rings or wedge voidsrepresents serious defects in the PCB's, especially in an era whenincreasingly high quality and reliability are demanded in the PCBindustry. Thus, there is a need for an improved alternative oxidecoating process that provides a surface that is less susceptible tochemical attack during post-lamination processing steps.

BRIEF SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide a copper surfaceroughening process that does not require mechanical roughening of thecopper surface.

Another object is to provide a copper surface roughening process thatdoes not suffer from the uniformity problems of conventional oxideprocesses.

A further object is to provide a copper surface roughening process thatdoes not require multiple passes or high temperature.

Yet another object is to provide a copper surface roughening processthat provides a surface that is less susceptible to chemical attackduring post-lamination processing steps.

A further object is to provide an improved alternative oxide coatingprocess and composition that provides a surface that is less susceptibleto chemical attack during post-lamination processing steps than at leastsome other alternative oxide coating processes and compositions.

A yet further object is to provide a copper surface roughening processthat provides a surface that is more acid resistant duringpost-lamination processing steps.

Another object is to provide an improved alternative oxide coatingprocess and composition that provides a surface that is more acidresistant during post-lamination processing steps than at least someother alternative oxide coating processes and compositions.

At least one of these objects is addressed, in whole or in part, by thepresent invention. In one embodiment, the invention is a composition andmethod for roughening a copper surface in order to provide higher bondstrengths between the copper and dielectric resin layers in a multilayerPCB, where such bonds are also resistant to chemical attack. Thecomposition comprises an oxidizer, a pH adjuster, a topography modifier,and a coating stabilizer. In another embodiment, the invention is aprocess for preparing roughened copper surfaces suitable for subsequentmultilayer lamination. The process involves contacting a copper surfacewith an adhesion promoting composition under conditions effective toprovide a roughened copper surface, and then contacting the roughenedcopper surface with an acid resistance promoting composition.

DETAILED DESCRIPTION OF THE INVENTION

While the invention will be described in connection with severalembodiments, it will be understood that the invention is not limited tothose embodiments. On the contrary, the invention includes allalternatives, modifications, and equivalents as may be included withinthe spirit and scope of the appended claims.

As noted above, one aspect of the present invention is an adhesionpromoting composition which provides a roughened copper surface,comprising an oxidizer, a pH adjuster, a topography modifier, and acoating stabilizer.

Any suitable oxidizer known in the art may be used in the inventivecomposition. Suitable oxidizers include hydrogen peroxide. The oxidizermay be present in the range between about 0.05 wt % and about 5 wt %,alternatively in the range between about 0.1 wt % and about 4 wt %. Asyet another alternative, the oxidizer may be present in the rangebetween about 0.5 wt % and about 3 wt %, alternatively in the rangebetween about 0.5 wt % and about 2 wt %. Proportions of oxidizer in thisspecification are based on undiluted quantities, although it will berecognized that, in practice, the oxidizers are typically part of anaqueous solution when added to the composition.

If hydrogen peroxide is used as the oxidizer, a hydrogen peroxidestabilizer may be used (although the use of a stabilizer is not requiredto practice this invention). Non-limiting examples of optional hydrogenperoxide stabilizers include: alkyl monoamines having 2 to 10 carbonatoms, and their salts; polymethylenediamines having 4 to 12 carbonatoms and their salts; alkoxyamines formed by substituting at least onehydrogen atom of ammonia by an alkoxy radical having 2 to 6 carbon atomsand alkoxyamines formed by substituting at least one hydrogen atomconnected with the nitrogen atom of an alkyl monoamine having 2 to 10carbon atoms by an alkoxy radical having 2 to 6 carbon atoms; alkyl acylradical formed by substituting at least one hydrogen atom of ammonia byan alkyl acyl radical having 3 to 6 carbon atoms, and at least one alkylacid amide formed by substituting at least one alkyl monoamine having 2to 10 carbon atoms by an alkyl acyl radical having 3 to 6 carbon atoms;alicyclic imines having a 5 to 8 membered ring; mono-n-propylamine,di-n-propylamine, tri-n-propylamine and hexamethylenediamine;octylamine; and propionylamide. In addition, U.S. Pat. Nos. 3,756,957,and 5,800,859 describe a range of suitable hydrogen peroxidestabilizers; U.S. Pat. Nos. 3,756,957 and 5,800,859 are herebyincorporated by reference in their entirety. An example of a suitablehydrogen peroxide stabilizer from the categories in these patents issodium phenolsulfonate.

If a hydrogen peroxide stabilizer is used, it may be present in thecomposition in an amount of from about 0.001 wt % to about 5 wt %,alternatively in an amount of from about 0.005 wt % to about 1 wt %.Alternatively, the hydrogen peroxide stabilizer may be present in thecomposition in an amount effective to achieve the purpose of stabilizingthe hydrogen peroxide to the desired degree.

The choice of pH adjuster is not critical. Any suitable organic orinorganic acid may be used, although nitric acid is not preferred.Non-limiting examples of suitable acids include sulfuric, phosphoric,acetic, formic, sulfamic, hydroxy-acetic acid, and mixtures thereof.Alternatively, sulfuric acid may be selected as the pH adjuster. The pHadjuster may be present in the composition in the range between about0.01% and about 20% by weight and alternatively in the range betweenabout 0.5% and about 10% by weight.

Suitable topography modifiers are five membered aromatic fusedN-heterocyclic ring compounds (hereinafter “N-heterocyclic compounds”)with at least one nitrogen atom in the N-heterocyclic ring:

In the above formula, X may be N or C, and Y may be N or C. The Rsubstituents on the aromatic ring may be H, halogen, hydroxy, alkyl,hydroxyalkyl, amino, aminoalkyl, nitro, nitroalkyl, mercapto,mercaptoalkyl, or alkoxy groups containing from 1 to about 10 or morecarbon atoms. Specific examples of alkyl groups include methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, amyl, etc. At leastone of the nitrogen atoms in the heterocyclic ring depicted above isbonded directly to a hydrogen atom. The nitrogen atom at the #1 positionin the heterocyclic ring is preferably, but not necessarily, bonded to ahydrogen atom. Non-limiting examples of suitable topography modifiersinclude 1H-benzotriazole (CAS registration number, “CAS”: 95-14-7),1H-Indole (CAS 120-72-9), 1H-indazole (CAS 271-44-3), and1H-benzimidazole (CAS 51-17-2). Derivatives of N-heterocyclic compoundssuitable as topography modifiers include N-heterocyclic compounds with ahydrogen atom bonded to the nitrogen atom at the #1 position in theheterocyclic ring.

Non-limiting examples of suitable derivatives of 1H-benzotriazole (CAS95-14-7) suitable for use as topography modifiers include:5-methyl-1H-benzotriazole (CAS 136-85-6), 6-Nitro-1H-benzotriazole (CAS2338-12-7), 1H-naphtho(1,2-d)triazole (CAS 233-59-0), and1H-Naphtho[2,3-d]triazole (CAS 269-12-5).

Non-limiting examples of suitable derivatives of indole (1H-Indole; CAS120-72-9) suitable for use as topography modifiers include:5-Aminoindole (1H-Indol-5-amine; CAS 5192-03-0), 6-methylindole(1H-Indole, 6-methyl-; CAS 3420-02-8), 1H-Indole-5-methyl (CAS614-96-0), 7-methylindol (1H-Indole, 7-methyl-; CAS 933-67-5),3-methylindole (1H-Indole, 3-methyl-; CAS 83-34-1), 2-Methylindole(2-Methyl-1H-Indole; CAS 95-20-5), 1H-Indole, 3,5-dimethyl-(CAS3189-12-6), 2,3-Dimethylindole (1H-Indole, 2,3-dimethyl-; CAS 91-55-4),and 2,6-dimethylindole (1H-Indole, 2,6-dimethyl-; CAS 5649-36-5).

Non-limiting examples of suitable derivatives of 1H-indazole (CAS271-44-3) suitable for use as topography modifiers include:1H-Indazol-5-amine (CAS 19335-11-6) and 3-Chloro-1H-indazole (CAS29110-74-5).

Non-limiting examples of suitable derivatives of 1H-benzimidazole (CAS51-17-2) suitable for use as topography modifiers include:2-Hydroxy-1H-benzimidazole (CAS 615-16-7), 2-Methyl-1H-benzimidazole(CAS 615-15-6), and 2-(methylthio)-1H-Benzimidazole (CAS 7152-24-1).

The topography modifier may be present in the range between about 0.1g/l (grams per liter) and about 20 g/l, alternatively in the rangebetween about 0.5 g/l and about 7 g/l. For example, 1H-benzotriazole canbe present in the range between about 0.1 g/l and about 20 g/l,alternatively in the range between about 0.5 g/l and about 7 g/l.

The topography modifier is thought to vary the surface characteristicsof the copper during treatment of the copper surface with the adhesionpromoting solution of the invention. During treatment with the adhesionpromoting composition of the invention, the copper surface is believedto comprise a complex of copper together with the topography modifier toproduce a greater surface area than would be possible without thetopography modifier. As a result, the topography modifier has abeneficial effect on peel strength—indeed, peel strength is dramaticallyreduced if the topography modifier is not used in the adhesion promotingsolution. The inventors do not intend the foregoing theory to limit theinvention to processes or products that operate as specified by thistheory. Any inaccuracy in this theory does not limit the scope of thepresent invention.

The coating stabilizer is a sulfur compound that renders the roughenedcopper surface more chemically resistant to subsequent chemicalprocessing. A suitable coating stabilizer may have the followingformula:

wherein Z₁, is H, Li, Na, K, NH₄,

wherein X₁ is S or N—R₉, and wherein X₂ is S or N—R₁₀. The R groups areindependently selected from H, halogen, S, epoxide, glycol, hydroxy,aryloxy, benzyloxy, alkoxy, haloalkoxy, amino, monoalkylamino,dialkylamino, heteroalkylamino, acyloxy, acyl, ketone, quinone,aldehyde, carbohydrate, organometallic, a C₁ up to C₁₈ alkyl which islinear or branched and may be singly or multiply substituted in singularor multiply bonded fashion, a cycloalkyl which may be singly or multiplysubstituted in singular or multiply bonded fashion, a heterocyclic whichmay be singly or multiply substituted in singular or multiply bondedfashion, a C₁ up to C₁₈ alkenyl which is linear or branched and may besingly or multiply substituted in singular or multiply bonded fashion, aC₁ up to C₁₈ alkadienyl which is linear or branched and may be singly ormultiply substituted in singular or multiply bonded fashion, a C₁ up toC₁₈ alkynyl which is linear or branched and may be singly or multiplysubstituted in singular or multiply bonded fashion, an aryl which may besingly or multiply substituted in singular or multiply bonded fashion, aheteroaryl which may be singly or multiply substituted in singular ormultiply bonded fashion, an alkylaryl which may be singly or multiplysubstituted in singular or multiply bonded fashion, an arylalkyl whichmay be singly or multiply substituted in singular or multiply bondedfashion, and combinations thereof, wherein the substituents are selectedfrom the group consisting of halogen, epoxide, glycol, N, O, S,haloalkyl, hydroxy, aryloxy, benzyloxy, alkoxy, haloalkoxy, amino,monoalkylamino, dialkylamino, heteroalkylamino, acyloxy, acyl, ketone,quinone, aldehyde, carbohydrate, organometallic, alkyl, aryl, andcombinations thereof. In addition, any two or more of R₁₋₁₀ may form alinkage or linkages comprising any of the groups identified abovesuitable for forming such linkages. Depending on the linkage, some ofR₁₋₁₀ may drop out. For example, if R₂ and R₃ form an aromatic linkagesuch as a benzene ring, then R₁ and R₄ will be nothing. The same holdstrue for the remainder of R₁₋₈: one substituent of each pair R₁ and R₂,R₃ and R₄, R₅ and R₆, and R₇ and R₈ will be nothing if the othersubstituent in the pair is part of an aromatic linkage.

Suitable coating stabilizers falling within formula (I) include thefollowing: 2-mercapto benzothiazole; 2,2′-dithiobis(benzothiazole);6-ethoxy-2-mercaptobenzothiazole; 2-mercaptothiazoline; and3,4,5,6-tetrahydro-2-pyrimidinethiol. Alternatively,2-mercaptothiazoline may be used as the coating stabilizer.

The coating stabilizer may, in the alternative, have the followingformula:

wherein Z₁ is Li, Na, K, NH₄, R₃,

wherein Z₂ is Li, Na, K or NH₄, wherein X₁ is S or N—R₆, and wherein X₂is S or N—R₇. The R groups are independently selected from H, halogen,S, epoxide, glycol, hydroxy, aryloxy, benzyloxy, alkoxy, haloalkoxy,amino, monoalkylamino, dialkylamino, heteroalkylamino, acyloxy, acyl,ketone, quinone, aldehyde, carbohydrate, organometallic, a C₁ up to C₁₈alkyl which is linear or branched and may be singly or multiplysubstituted in singular or multiply bonded fashion, a cycloalkyl whichmay be singly or multiply substituted in singular or multiply bondedfashion, a heterocyclic which may be singly or multiply substituted insingular or multiply bonded fashion, a C₁ up to C₁₈ alkenyl which islinear or branched and may be singly or multiply substituted in singularor multiply bonded fashion, a C₁ up to C₁₈ alkadienyl which is linear orbranched and may be singly or multiply substituted in singular ormultiply bonded fashion, a C₁ up to C₁₈ alkynyl which is linear orbranched and may be singly or multiply substituted in singular ormultiply bonded fashion, an aryl which may be singly or multiplysubstituted in singular or multiply bonded fashion, a heteroaryl whichmay be singly or multiply substituted in singular or multiply bondedfashion, an alkylaryl which may be singly or multiply substituted insingular or multiply bonded fashion, an arylalkyl which may be singly ormultiply substituted in singular or multiply bonded fashion, andcombinations thereof, wherein the substituents are selected fromhalogen, epoxide, glycol, N, O, S, haloalkyl, hydroxy, aryloxy,benzyloxy, alkoxy, haloalkoxy, amino, monoalkylamino, dialkylamino,heteroalkylamino, acyloxy, acyl, ketone, quinone, aldehyde,carbohydrate, organometallic, alkyl, aryl, and combinations thereof. Inaddition, any two or more of R₁₋₇ may form a linkage or linkagescomprising any of the groups identified above suitable for forming suchlinkages.

Suitable coating stabilizers falling within formula (II) include thefollowing: 2-imidazolidinethione; potassium3-(thiocarbamoyl)-dithiocarbazate; sodium diethyldithiocarbamate; sodiumdimethyldithiocarbamate; tetraethylthiuram disulfide; tetramethylthiuramdisulfide; and 2,5-dithiobiurea. Alternatively, sodiumdiethyldithiocarbamate may be used as the coating stabilizer.

The coating stabilizer may be present in the composition in the rangebetween about 1 to about 1000 ppm, alternatively in the range betweenabout 2 to about 200 ppm, alternatively in the range between about 50 toabout 150 ppm, alternatively about 100 ppm. For example,2-mercaptothiazoline can be present at about 100 ppm.

The inventive composition for roughening a copper surface may alsooptionally include a uniformity enhancer and/or a coating promoter. Theoptional uniformity enhancer may be a tetrazole such as 1H-tetrazole(CAS 288-94-8) and its derivatives:

The R1 and R2 substituents on the tetrazole ring may be hydroxyl, amino,alkyl, hydroxyalkyl, aminoalkyl, nitroalkyl, mercaptoalkyl, or alkoxygroups containing from 1 to about 10 or more carbon atoms. Specificexamples of alkyl groups include methyl, ethyl, propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, amyl, etc. Non-limiting examples ofsuitable tetrazole derivatives that can be used in the present inventionas a uniformity enhancer include: 5-aminotetrazole (CAS 5378-49-4),5-methyltetrazole (CAS 4076-36-2), 5-methylaminotetrazole (CAS53010-03-0), 1H-tetrazol-5-amine (CAS 4418-61-5), 1H-tetrazol-5-amine,N,N-dimethyl-(CAS 5422-45-7), 1-methyltetrazole (CAS 16681-77-9),1-methyl-5-mercaptotetrazole, 1,5-dimethyltetrazole (CAS 5144-11-6),1-methyl-5-aminotetrazole (CAS 5422-44-6), and1-methyl-5-methylamino-tetrazole (CAS 17267-51-5).

The optional uniformity enhancer may be present in an amount effectiveto enhance the uniformity of the roughened copper surface.Alternatively, the uniformity enhancer may be present in the rangebetween about 0.01 to about 10 g/l, alternatively in the range betweenabout 0.1 to about 5 g/l, alternatively in the range between about 0.3to about 1 g/l, alternatively at about 0.5 g/l. For example,5-aminotetrazole can be present at about 0.5 g/l.

The optional coating promoter is a five membered aromatic fusedN-heterocyclic ring compound with 1 to 3 nitrogen atoms in the fusedring, wherein none of the 1 to 3 nitrogen atoms in the fused ring arebonded to a hydrogen atom:

In the above formula, X may be N or C, and Y may be N or C. The Rsubstituents on the aromatic ring may be H, halogen, hydroxy, alkyl,hydroxyalkyl, amino, aminoalkyl, nitro, nitroalkyl, mercapto,mercaptoalkyl, or alkoxy groups containing from 1 to about 10 or morecarbon atoms. The R1 substituents on the heterocyclic ring bonded to thenitrogen atom at the #1 position may be hydroxyl, amino, alkyl,hydroxyalkyl, aminoalkyl, nitroalkyl, mercaptoalkyl, or alkoxy groups.Specific examples of alkyl groups include methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, amyl, etc. Non-limitingexamples of optional coating promoters suitable for use in the presentinvention include: 1-hydroxybenzotriazole (CAS 2592-95-2),1-methylindole (CAS 603-76-9), 1-methylbenzotriazole (CAS 13351-73-0),1-methylbenzimidazole (CAS 1632-83-3), 1-methylindazole (CAS13436-48-1), 1-ethyl-indazole (CAS 43120-22-5), 1H-Indole,1,5-dimethyl-indole (CAS 27816-53-1), 1,3-dimethyl-indole (CAS875-30-9), methyl 1-(butylcarbamoyl)-2-benzimidazolecarbonate,1-(chloromethyl)-1H-benzotriazole, and 1-aminobenzotriazole.

The optional coating promoting may be present in an amount effective toenhance the coating characteristics of the composition. Alternatively,the coating promoter may be present in the range between about 0.01 toabout 10 g/l, alternatively in the range between about 0.1 to about 5g/l, alternatively in the range between about 0.3 to about 3 g/l,alternatively at about 2 g/l. For example, 1-hydroxybenzotriazole can bepresent at about 2 g/l.

The formulation of the inventive composition for roughening a coppersurface may be made up with de-ionized water.

The inventive composition for roughening a copper surface does notrequire halogen ions and can be free of halogen ions, if desired. Theinventors define “halogen ions” as fluoride, chloride, bromide or iodideions or any combination or equivalent of these ions in aqueous solution.In addition, the composition of the present invention does not require asurfactant to achieve an excellent roughened copper surface.

Halogens can, however, be employed in the formulation if desired. Forexample, a small amount of chloride ion or other halide ions can be usedin the formulation. If employed, halide ions may be present in the rangebetween about 0.1 ppm to about 1000 ppm, alternatively in the rangebetween about 1 ppm to about 100 ppm.

The adhesion promoting composition may optionally comprise a copper saltsuch as copper sulfate. The aqueous copper ions protect virgin stainlesssteel surfaces, such as those of a process tank, from chemical attack.Hence it is advantageous to include a quantity of copper salt in theadhesion promoting composition if the copper surface to be treated isdipped into a new or previously unused steel tank. However, there is norequirement to include a copper salt to obtain a highly satisfactoryroughened copper surface.

The adhesion promoting composition may also optionally contain a watersoluble polymer. Any water soluble polymer known in the art may be usedin the present adhesion promoting composition. Suitable water solublepolymers include polymers of ethylene oxide and propylene oxide,polyethylene glycols, polypropylene glycols, and polyvinyl alcohols. Thewater soluble polymer may be present in the range of between about 0.01wt % and about 5 wt %, alternatively in the range of between about 0.05wt % and about 3 wt %, alternatively in the range of between about 0.1wt % and about 1 wt %, alternatively at about 0.5 wt %. Polyethyleneglycol may be selected as the optional water soluble polymer. Onesuitable source of polyethylene glycol is the product Pluracol® E2000sold by the BASF Corporation.

A copper surface can be treated with the adhesion promoting compositionin a variety of ways, including (but not limited to) immersion in abath, dipping in a bath, or spraying. The treatment may take place atany temperature and for any duration suitable to obtain the desireduniformed roughened copper surface. For example, suitable roughenedcopper surfaces may be obtained where the temperature during treatmentis in the range from about 40° F. to about 180° F. (about 4° C. to about82° C.), alternatively from about 70° F. to about 150° F. (about 21° C.to about 66° C.), alternatively from about 80° F. to about 120° F.(about 27° C. to about 49° C.), alternatively about 100° F. (about 38°C.). Suitable roughened copper surfaces may also be obtained withtemperatures outside of these ranges, however. With respect to duration,the adhesion promoting composition may, for example, be contacted withthe copper surface for about 1 second to about 1 hour, alternativelyfrom about 10 seconds to about 10 minutes, alternatively from about 30seconds to about 5 minutes, alternatively for about 1 minute. Suitableroughened copper surfaces may also be obtained with contact durationsoutside of these ranges, however.

In keeping with another aspect of the present invention, the process ofpreparing roughened copper surfaces suitable for subsequent multilayerlamination includes the following steps, some of which are optional:

-   -   (i) Providing a substantially clean copper surface, optionally        by applying a highly built alkaline cleaning solution to a        copper surface. The highly built alkaline cleaning solution        comprises a surfactant and a phosphate or a phosphate ester.    -   (ii) Optionally dipping the substantially clean copper surface        into a pre-dip to condition the surface and/or to remove surplus        cleaning solution from the copper surface providing a clean        copper surface. One suitable optional pre-dip may comprise an        oxidizer, a pH adjuster and a topography modifier, as those        components are described above. The oxidizer and topography        modifier may be in the pre-dip in the ranges described above.        The pH adjuster may be in the pre-dip in the range between about        0.005% and about 10% by weight and alternatively in the range        between about 0.01% and about 5% by weight. A hydrogen peroxide        stabilizer may be used if hydrogen peroxide is used as the        oxidizer. The hydrogen peroxide stabilizer may be selected from        the various stabilizers described above and may be in the        pre-dip in the ranges described above. Other suitable pre-dips        that will be known to those of skill in the art may also be        used. The pre-dip treatment may take place at any temperature        and for any duration suitable to obtain the desired conditioning        and/or cleaning, including the temperatures and durations        discussed above for application of the adhesion promoting        composition.    -   (iii) Applying to the clean copper surface an adhesion promoting        composition comprising an oxidizer, a pH adjuster, a topography        modifier, a coating stabilizer, and optionally, other optional        components as described above.    -   (iv) Optionally dipping the uniformly roughened copper surface        into a post-dip to provide a roughened copper surface suitable        for subsequent multilayer lamination. The optional post-dip is        used to coat the roughened copper surface with a coating of        organic molecules to enable enhanced bonding between the        roughened copper surface and a suitable dielectric resin. The        post-dip solution comprises an azole or silane compound. The        post-dip may further comprise a titanate, zirconate, or        aluminate.        Step (i) may further include draining excess cleaning solution        from the copper surface.

Non-limiting examples of silanes for enhancing the bond strength betweenthe copper surface and the dielectric include any trichloro ortrimethoxy silane, especially those derivatives with at least onenitrogen atom such as trimethoxysilylpropyldiethylenetriamine. Otherexamples of silanes suitable for use in the present invention include:

-   -   3-methylacryloyloxypropyltrimethoxysilane,    -   3-(N-styrylmethyl-2aminoethylamino) propyltrimethoxysilane        hydrochloride,    -   3-(N-allyl-2-aminoethylamino)-propyltrimethoxysilane        hydrochloride,    -   N-(styrylmethyl)-3-aminopropyltrimethoxysilane hydrochloride,    -   N-2-aminoethyl-3-aminopropyltrimethoxysilane,    -   3-(N-Benzyl-2-aminoethylamino)-propyltrimethoxy silane        hydrochloride,    -   beta-(3,4-epoxycyclohexyl) ethyltrimethoxysilane,        gamma-aminopropyl-triethoxy silane,    -   gamma-glycidoxypropyltrimethoxysilane, and    -   vinyltrimethoxysilane.

Non-limiting examples of titanates that can be used in the presentinvention include:

-   -   titanate amine,    -   tetraocytl di(ditridecyl)phosphito titanate,    -   tetra(2,2-diallyloxymethyl) butyl-di(ditridecyl)phosphito        titanate,    -   neopentyl(diallyl)oxytri(diocytl)pryo-phosphato titante, and    -   neopentyl(diallyl)oxy tri(m-amino)phenyl titanate.

Non-limiting examples of suitable zirconates (available, for example,from Kenrich Petrochemicals, Inc., Bayonne, N.J.) include:

-   -   KZ 55-tetra (2,2 diallyloxymethyl)butyl,    -   di(ditridecyl)phosphito zirconate,    -   NZ-01-neopentyl(diallyl)oxy,    -   trineodecanoyl zirconate, and    -   NZ-09-neopentyl(diallyl)oxy, tri(dodecyl)benzene-sulfonyl        zirconate.

Further non-limiting examples of suitable zirconates include: tetra (2,2diallyloxymethyl)butyl-di(ditridecyl)phosphito zirconate, and zirconiumIV 2,2-dimethyl 1,3-propanediol.

Non-limiting examples of aluminates that can be used in the presentinvention include: Kenrich® diisobutyl(oleyl)acetoacetylaluminate (KA301), and diisopropyl(oleyl)acetoacetyl aluminate (KA 322).

The inventors have found that the use of a coating stabilizer in theinventive adhesion promoting composition, as described above, rendersthe coating on the copper surface more chemically resistant tosubsequent processing than alternative oxide coating processes known inthe art which do not use such stabilizer. Another aspect of the presentinvention is a process in which a copper surface is treated with anadhesion promoting composition in which a coating stabilizer isoptional, and then subsequently contacted with a composition thatpromotes acid resistance. In other words, the roughened copper surfaceis made resistant to chemical attack by a separate application of anacid resistance promoting composition after the adhesion promotingcomposition has been applied.

The inventors discovered that this two-step approach is particularlyadvantageous from a manufacturing standpoint. In particular, it wasdiscovered that some of the coating stabilizers described above arethemselves susceptible to chemical attack. When such coating stabilizersare added directly to an adhesion promoting bath which contains a pHadjuster, such as sulfuric acid, they tend to decompose over time intotheir synthetic components. After such decomposition, the baths nolonger produce an acid resistant coating on the copper surface.Typically, decomposition of the coating stabilizer occurs within 30minutes to 4 hours of addition. The cost associated with continuallyrefreshing the baths to avoid the effects of this decomposition renderthis process less desirable for commercial manufacturing purposes.

The inventive process which avoids these decomposition issues comprisesthe steps of (1) contacting with a clean copper surface an adhesionpromoting composition under conditions effective to provide a roughenedcopper surface, and (2) contacting the roughened copper surface with anacid resistance promoting composition.

The adhesion promoting composition is the same as that described above,with the exception that the coating stabilizer is an optional component,and is preferably absent. Thus, the adhesion promoting compositioncomprises an oxidizer, a pH adjuster, a topography modifier, and,optionally, a coating stabilizer as well as any of the other optionalcomponents described above. The adhesion promoting composition may beapplied to the copper surface in any of the various manners and underany of the various conditions described above.

Suitable acid resistance promoting compositions include thio compounds,particularly thiocarbamates, thiocarbonates, xanthates, and sulfides.Alternatively, the acid resistance promoting composition is asulfur-containing compound which may have the following formula:(S)_(A)—X₁  (III)wherein A is 1–20 (alternatively A may be 1–10 or 1–5) and X₁ is Mg, Ca,Li₂, Na₂, K₂, or (NH₄)₂. As yet another alternative, the acid resistancepromoting composition may have the following formula:

wherein A is 1–20 (alternatively A may be 1–10 or 1–5) and X₁ is Mg, Ca,Li₂, Na₂, K₂, or (NH₄)₂.

As yet another alternative, the acid resistance promoting compositionmay have the following formula:

wherein W₁ is

O—R₃, or S—R₃, wherein A is 1–20, wherein X₂ is Li, Na, K, NH₄,

wherein W₂ is

O—R₆, or S—R₆, and wherein B is 1–20. A may also be 1–10 or 1–5. R₅The R groups are independently selected from H, halogen, S, epoxide,glycol, hydroxy, aryloxy, benzyloxy, alkoxy, haloalkoxy, amino,monoalkylamino, dialkylamino, heteroalkylamino, acyloxy, acyl, ketone,quinone, aldehyde, carbohydrate, organometallic, a C₁ up to C₁₈ alkylwhich is linear or branched and may be singly or multiply substituted insingular or multiply bonded fashion, a cycloalkyl which may be singly ormultiply substituted in singular or multiply bonded fashion, aheterocyclic which may be singly or multiply substituted in singular ormultiply bonded fashion, a C₁up to C₁₈ alkenyl which is linear orbranched and may be singly or multiply substituted in singular ormultiply bonded fashion, a C₁ up to C₁₈ alkadienyl which is linear orbranched and may be singly or multiply substituted in singular ormultiply bonded fashion, a C₁ up to C₁₈ alkynyl which is linear orbranched and may be singly or multiply substituted in singular ormultiply bonded fashion, an aryl which may be singly or multiplysubstituted in singular or multiply bonded fashion, a heteroaryl whichmay be singly or multiply substituted in singular or multiply bondedfashion, an alkylaryl which may be singly or multiply substituted insingular or multiply bonded fashion, an arylalkyl which may be singly ormultiply substituted in singular or multiply bonded fashion, andcombinations thereof, wherein the substituents are selected from thegroup consisting of halogen, epoxide, glycol, N, O, S, haloalkyl,hydroxy, aryloxy, benzyloxy, alkoxy, haloalkoxy, amino, monoalkylamino,dialkylamino, heteroalkylamino, acyloxy, acyl, ketone, quinone,aldehyde, carbohydrate, organometallic, alkyl, aryl, and combinationsthereof. In addition, any two adjacent of R₁₋₆ may form a linkage orlinkages comprising any of the groups identified above suitable forforming such linkages.

Suitable acid resistance promoting compositions falling with formulas(III), (IV) and (V) above include: sodium dialkyl dithio carbamates,sodium dialkyl polythiocarbamates, sodium dialkyl trithio carbonates,sodium dialkyl polythiocarbonates, sodium diaryl dithio carbamates,sodium diaryl polythiocarbamates, sodium diaryl trithio carbonates,sodium diaryl polythiocarbonates, sodium alkylaryl dithio carbamates,sodium alkylaryl polythiocarbamates, sodium alkylaryl trithiocarbonates, sodium alkylaryl polythiocarbonates, potassium dialkyldithio carbamates, potassium dialkyl polythiocarbamates, potassiumdialkyl trithio carbonates, potassium dialkyl polythiocarbonates,potassium diaryl dithio carbamates, potassium diaryl polythiocarbamates,potassium diaryl trithio carbonates, potassium diarylpolythiocarbonates, potassium alkylaryl dithio carbamates, potassiumalkylaryl polythiocarbamates, potassium alkylaryl trithio carbonates,potassium alkylaryl polythiocarbonates, ammonium dialkyl dithiocarbamates, ammonium dialkyl polythiocarbamates, ammonium dialkyltrithio carbonates, ammonium dialkyl polythiocarbonates, ammonium diaryldithio carbamates, ammonium diaryl polythiocarbamates, ammonium diaryltrithio carbonates, ammonium diaryl polythiocarbonates, ammoniumalkylaryl dithio carbamates, ammonium alkylaryl polythiocarbamates,ammonium alkylaryl trithio carbonates, ammonium alkylarylpolythiocarbonates, dialkyl xanthates, diaryl xanthates, alkylarylxanthates, sulfide, disulfide, trisulfide, tetrasulfide, polysulfide,and combinations thereof, wherein the alkyl component is a C₁ up to C₁₈alkyl which is linear or branched and may be singly or multiplysubstituted in singular or multiply bonded fashion, wherein the arylcomponent is an aryl or a heteroaryl which may be singly or multiplysubstituted in singular or multiply bonded fashion, and wherein thesubstituents are selected from the group consisting of halogen, halide,epoxide, glycol, N, O, S, haloalkyl, hydroxy, aryloxy, benzyloxy,alkoxy, haloalkoxy, amino, monoalkylamino, dialkylamino,heteroalkylamino, acyloxy, acyl, ketone, quinone, aldehyde,carbohydrate, organometallic, alkyl, aryl, and combinations thereof.Several nonlimiting examples of suitable acid resistance promotingcompositions are sodium dioctyldithiocarbamate, disodiumtrithiocarbonate, sodium sulfide, sodium N,N-dibutyldithiocarbamate, andsodium hydroquinone monomethyl ether xanthate (“HQMME-xanthate”).

The acid resistance promoting composition may be contacted with theroughened copper surface in a variety of ways, including (but notlimited to) immersion in a bath, dipping in a bath, or spraying. Theacid resistance promoting composition may be contacted with theroughened copper surface as an aqueous solution. When applied in thisfashion, the composition may be present in the aqueous solution betweenabout 0.1 g/l and about 5 g/l. Alternatively, the composition may bepresent in the aqueous solution between about 1 g/l and about 3 g/l. Asyet another alternative, the composition may be present in the aqueoussolution at about 1 g/l.

The acid resistance promoting composition may be contacted with theroughened copper surface for at least about 1 second. Alternatively, thecomposition may be contacted with the roughened copper surface forbetween about 1 second to about 5 minutes. As yet another alternative,the composition may be contacted with the roughened copper surface forbetween about 5 seconds to about 2 minutes.

The acid resistance promoting composition may be contacted with theroughened copper surface at any temperature suitable to obtain thedesired acid-resistant roughened copper surface. For example, suitableroughened copper surfaces may be obtained where the temperature duringtreatment is in the range from about 20° F. to about 180° F. (about −7°C. to about 82° C.), alternatively from about 40° F. to about 150° F.(about 4° C. to about 66° C.), alternatively from about 60° F. to about120° F. (about 16° C. to about 49° C.), alternatively about 70° F.(about 21° C.), alternatively about room temperature. Suitableacid-resistant roughened copper surfaces may also be obtained withtemperatures outside of these ranges, however.

The process of preparing roughened copper surfaces and subsequently posttreating the surfaces with an acid resistance promoting composition mayalso include other optional steps. For instance, the process maycomprise the following steps, some of which are optional:

-   -   (i) Providing a substantially clean copper surface, optionally        by applying a highly built alkaline cleaning solution to a        copper surface. The highly built alkaline cleaning solution        comprises a surfactant and a phosphate or a phosphate ester.    -   (ii) Optionally dipping the substantially clean copper surface        into a pre-dip to condition the surface and/or to remove surplus        cleaning solution from the copper surface providing a clean        copper surface. One suitable optional pre-dip may comprise an        oxidizer, a pH adjuster and a topography modifier, as those        components are described above. The oxidizer and topography        modifier may be in the pre-dip in the ranges described above.        The pH adjuster may be in the pre-dip in the range between about        0.005% and about 10% by weight and alternatively in the range        between about 0.01% and about 5% by weight. A hydrogen peroxide        stabilizer may be used if hydrogen peroxide is used as the        oxidizer. The hydrogen peroxide stabilizer may be selected from        the various stabilizers described above and may be in the        pre-dip in the ranges described above. Other suitable pre-dips        that will be known to those of skill in the art may also be        used. The pre-dip treatment may take place at any temperature        and for any duration suitable to obtain the desired conditioning        and/or cleaning, including the temperatures and durations        discussed above for application of the adhesion promoting        composition.    -   (iii) Applying to the clean copper surface an adhesion promoting        composition comprising an oxidizer, a pH adjuster, a topography        modifier, optionally a coating stabilizer, and optionally, other        optional components as described above, in order to form a        roughened copper surface.    -   (iv) Optionally rinsing the roughened copper surface with water.    -   (v) Dipping the roughened copper surface in an aqueous solution        containing an acid resistance promoting composition, as        described above.    -   (vi) Optionally dipping the uniformly roughened copper surface        into a post-dip to provide a roughened copper surface suitable        for subsequent multilayer lamination. The optional post-dip is        used to coat the roughened copper surface with a coating of        organic molecules to enable enhanced bonding between the        roughened copper surface and a suitable dielectric resin. The        post-dip solution comprises an azole or silane compound. The        post-dip may further comprise a titanate, zirconate, or        aluminate.        Step (i) may further include draining excess cleaning solution        from the copper surface.

The inventors have found that the use of an adhesion promotingcomposition on a copper surface, followed by subsequent treatment withan acid resistance promoting composition, renders the coating on thecopper surface more chemically resistant to subsequent processing thanother alternative oxide coating processes known in the art. At the sametime, inefficiencies in the manufacturing process are avoided becausethe acid resistance promoting composition is applied in a separate stepand thus is not subject to untimely decomposition due to the acidicnature of the adhesion promoting composition bath.

One practical test that can be used to indicate the better adhesion ofresins to the present copper surface is a “peel strength” test.Self-adhesive tape is adhered to a treated copper surface which has beenlaminated to a polymeric substrate. The surface is placed into a nitricacid bath to remove the copper from the non-taped regions of thesubstrate. The tape is removed and the remaining copper is thenmechanically peeled away from the substrate while measuring the forceneeded to accomplish the peel in pounds per inch. Higher peel strengthsare typically indicative of a desirable, tightly-adhering coating.

One practical test that can be used to indicate the better resistance tochemical attack of the present copper surfaces is the simple applicationof an acid solution to the copper surfaces, followed by observation.Such test is described in further detail below in conjunction with theexamples.

The following examples represent specific but nonlimiting embodiments ofthe present invention:

EXAMPLE 1

A clean copper surface was prepared by treating a substantially cleancopper surface in a pre-dip bath at 70° F. (21° C.). The pre-dip bathcomprised 1.15 wt % H₂O₂, 0.05 wt % sodium phenolsulfonate, 0.13 wt %H₂SO₄, 0.18 wt % benzotriazole (1.8 g/l), balance deionized water. Theclean copper surface was removed from the pre-dip bath after one minute.

The clean copper surface was then treated in a bath comprising 1.42 wt %H₂O₂ (oxidizer), 0.06 wt % sodium phenolsulfonate (H₂O₂ stabilizer),8.61 wt % H₂SO₄ (pH adjuster), 0.57 wt % benzotriazole (“BTA”)(topography modifier), 0.0017 wt % NaCl (chloride ion), 0.38 wt %polyethylene glycol, balance deionized water (see Table 1). The bathtemperature was maintained at 100° F. (38° C.). The copper surface wasremoved from the bath after one minute, rinsed with deionized water, anddried with an air hose. A roughened texture was observed on the coppersurface, as is consistent with an alternative oxide coating process.Using an eye-dropper, a solution containing 15% by volume hydrochloricacid was applied to the roughened surface. The roughened surfaceimmediately dissolved, revealing bare copper beneath.

EXAMPLE 2

A clean copper surface was treated in a bath comprising 1.42 wt % H₂O₂,0.06 wt % sodium phenolsulfonate, 8.61 wt % H₂SO₄, 0.57 wt % BTA, 0.0017wt % (17ppm) NaCl, 0.38 wt % polyethylene glycol, 1 ppm sodiumdiethyl-dithiocarbamate (“SDDC”) (a coating stabilizer), balancedeionized water (see Table 1). The bath temperature was maintained at100° F. (38° C.). The copper surface was removed from the bath after oneminute, rinsed with deionized water, and dried with an air hose. Aroughened texture was observed on the copper surface, as is consistentwith an alternative oxide coating process. Using an eye-dropper, asolution containing 15% by volume hydrochloric acid was applied to theroughened surface. The roughened surface dissolved over the course of10–20 seconds, revealing bare copper beneath. The fact that the surfacedid not dissolve immediately demonstrates that the roughened surface wasmore chemically resistant than the roughened surface of Example 1, whichwas not prepared with a coating stabilizer.

EXAMPLE 3

A roughened copper surface was prepared in the same manner as Example 2,with the exception that the bath contained 5 ppm SDDC (see Table 1).Upon applying a 15% hydrochloric acid solution, the roughened surfacedissolved over the course of 20–30 seconds, revealing bare copperbeneath. The increased time for the roughened surface to dissolvedemonstrates the improved chemical resistance of the surface.

EXAMPLE 4

A roughened copper surface was prepared in the same manner as Example 2,with the exception that the bath contained 20 ppm SDDC (see Table 1).Upon applying a 15% hydrochloric acid solution, the roughened surfacedissolved over the course of 50–70 seconds, revealing bare copperbeneath. Again, the increased time for the roughened surface to dissolvedemonstrates the improved chemical resistance of the surface.

EXAMPLE 5

A roughened copper surface was prepared in the same manner as Example 2,with the exception that the bath contained 100 ppm SDDC (see Table 1). A15% hydrochloric acid solution was applied to the roughened surface.After three to five minutes, the roughened surface was intact and nobare copper was visible. This demonstrates exceptional acid resistancecompared to the surface of Example 1, which was prepared without acoating stabilizer.

See Table 1 for a summary of examples 1 to 5.

EXAMPLES 6 THROUGH 11

Adhesion promoting compositions similar to those tested in Examples 1–5were used to prepare roughened copper surfaces, which were then testedfor peel strength. Specifically, for each of Examples 6–11, a cleancopper surface was treated in a bath comprising 1.42 wt % H₂O₂, 0.06 wt% sodium phenolsulfonate, 8.61 wt % H₂SO₄, 0.57 wt % BTA, 0.0017 wt %(17ppm) NaCl, 0.38 wt % polyethylene glycol, and deionized water. InExample 6, no coating stabilizer was used. The bath of Example 7contained 1 ppm SDDC, the bath of Example 8 contained 5 ppm SDDC, thebath of Example 9 contained 10 ppm SDDC, the bath of Example 10contained 50 ppm SDDC, and the bath of Example 11 contained 100 ppmSDDC. Peel strength testing demonstrated that the copper surfacesprepared in each of Examples 6–11 exhibited a desirable,tightly-adhering coating. While the data did not show a trend towardsimproved peel strength with increasing concentrations of coatingstabilizer, the data did demonstrate that the use of a coatingstabilizer does not negatively impact the peel strength of the roughenedcopper surface.

Following peel strength testing, the roughened copper surfaces ofExamples 6–11 were laminated to an FR4 substrate using a pressure of 292psi for 60 minutes at 350° F. (177° C.). Subsequent testing onhand-drilled holes through the laminated sandwiches demonstratedsignificant interconnect etch back for Examples 7 and 11, but none ofthe sandwiches exhibited any pink ring or wedge attack.

EXAMPLE 12

A clean copper surface was treated in a bath comprising 1.42 wt % H₂O₂,0.06 wt % sodium phenolsulfonate, 8.61 wt % H₂SO₄, 0.57 wt % BTA, 0.0017wt % (17 ppm) NaCl, 0.38 wt % polyethylene glycol, 1 ppm2-mercaptothiazoline (“MTZ”) (a coating stabilizer), balance deionizedwater (see Table 2). The bath temperature was maintained at 100° F. (38°C.). The copper surface was removed from the bath after one minute,rinsed with deionized water, and dried with an air hose. A roughenedtexture was observed on the copper surface, as is consistent with analternative oxide coating process. Using an eye-dropper, a solutioncontaining 15% by volume hydrochloric acid was applied to the roughenedsurface. The roughened surface dissolved over the course of 10–20seconds, revealing bare copper beneath. The fact that the surface didnot dissolve immediately demonstrates that the roughened surface wasmore chemically resistant than the roughened surface of Example 1, whichwas not prepared with a coating stabilizer.

EXAMPLE 13

A roughened copper surface was prepared in the same manner as Example12, with the exception that the bath contained 5 ppm MTZ (see Table 2).Upon applying a 15% hydrochloric acid solution, the roughened surfacedissolved over the course of 40–60 seconds, revealing bare copperbeneath. The increased time for the roughened surface to dissolvedemonstrates the improved chemical resistance of the surface.

EXAMPLE 14

A roughened copper surface was prepared in the same manner as Example12, with the exception that the bath contained 20 ppm MTZ (see Table 2).Upon applying a 15% hydrochloric acid solution, the roughened surfacedissolved over the course of 70–90 seconds, revealing bare copperbeneath. Again, the increased time for the roughened surface to dissolvedemonstrates the improved chemical resistance of the surface.

EXAMPLE 15

A roughened copper surface was prepared in the same manner as Example12, with the exception that the bath contained 100 ppm MTZ (see Table2). A 15% hydrochloric acid solution was applied to the roughenedsurface. After three to five minutes, the roughened surface was intactand no bare copper was visible. This demonstrates exceptional acidresistance compared to the surface of Example 1, which was preparedwithout a coating stabilizer.

See Table 2 for a summary of examples 12 to 15.

EXAMPLES 16 THROUGH 25

For examples 16 through 25, a clean copper surface is treated in a bathcomprising 1.42 wt % H₂O₂, 0.06 wt % sodium phenolsulfonate, 8.61 wt %H₂SO₄, 0.57 wt % BTA, 0.0017 wt % (17ppm) NaCl, 0.38 wt % polyethyleneglycol, 100 ppm of a coating stabilizer, balance deionized water. Thecoating stabilizer used for each example is listed in Table 3. Thecopper surface is removed from the bath after one minute, rinsed withdeionized water, and dried with an air hose. A roughened texture isobserved on the copper surface, as is consistent with an alternativeoxide coating process. Using an eye-dropper, a solution containing 15%by volume hydrochloric acid is applied to the roughened surface. Theroughened copper surface of each of Examples 16 through 25 exhibitsimproved acid resistance compared to the surface of Example 1, which wasprepared without a coating stabilizer.

EXAMPLES 26 THROUGH 31

In Examples 26 through 31, a clean copper surface is treated in a bathcomprising 1.42 wt % H₂O₂, 0.06 wt % sodium phenolsulfonate, 8.61 wt %H₂SO₄, 0.0017 wt % (17ppm) NaCl, 0.38 wt % polyethylene glycol, 100 ppmMTZ, a topography modifier, optionally a uniformity enhancer and/orcoating promoter, balance deionized water. Table 4 lists the topographymodifier and optional uniformity and/or coating promoter used in each ofExamples 26 through 31.

The copper surface is removed from the bath after one minute, rinsedwith deionized water, and dried with an air hose. A roughened texture isobserved on the copper surface, as is consistent with an alternativeoxide coating process. Using an eye-dropper, a solution containing 15%by volume hydrochloric acid is applied to the roughened surface. Theroughened copper surface of each of Examples 26 through 31 is desirablyuniformly etched and coated, and exhibits improved acid resistancecompared to the surface of Example 1, which was prepared without acoating stabilizer.

EXAMPLE 32

A clean copper surface is treated in a bath comprising 1.42 wt % H₂O₂,8.61 wt % H₂SO₄, 0.57 wt % BTA, 0.5 g/l 5-aminotetrazole (uniformityenhancer), 100 ppm MTZ, balance deionized water. The copper surface isremoved from the bath after one minute, rinsed with deionized water, anddried with an air hose. A roughened texture is observed on the coppersurface, as is consistent with an alternative oxide coating process.Using an eye-dropper, a solution containing 15% by volume hydrochloricacid is applied to the roughened surface. The roughened copper surfaceis desirably uniformly etched, and exhibits improved acid resistancecompared to the surface of Example 1, which was prepared without acoating stabilizer.

EXAMPLE 33

A roughened copper surface was prepared in the same manner as Example32, with the exception that 0.5 g/l 1-hydroxybenzotriazole (coatingpromoter) is used in the bath instead of 0.5 g/l 5-aminotetrazole(uniformity enhancer). The roughened copper surface is desirably coated,and exhibits improved acid resistance compared to the surface of Example1, which was prepared without a coating stabilizer.

EXAMPLE 34

A clean copper surface was prepared by treating a substantially cleancopper surface in a pre-dip bath at 70° F. (21° C.). The pre-dip bathcomprised 1.15 wt % H₂O₂, 0.05 wt % sodium phenolsulfonate, 0.13 wt %H₂SO₄, 0.18 wt % BTA (1.8 g/l), balance deionized water. The cleancopper surface was removed from the pre-dip bath after one minute.

The clean copper surface was then treated in a bath comprising 1.42 wt %H₂O₂, 0.06 wt % sodium phenolsulfonate, 8.61 wt % H₂SO₄, 0.57 wt %benzotriazole BTA, 0.0017 wt % NaCl, 0.38 wt % polyethylene glycol,balance deionized water. The bath temperature was maintained at 100° F.(38° C.). The copper surface was removed from the bath after one minute,rinsed with deionized water, and dried with an air hose. A roughenedtexture was observed on the copper surface, as is consistent with analternative oxide coating process.

The roughened copper surface was then dipped into a post-treatment bathcomprising 1 g/l disodium trithiocarbonate (an acid resistance promotingcomposition) and the balance deionized water. The bath temperature wasmaintained at room temperature. The roughened copper surface was removedfrom the bath after 15 seconds, rinsed with deionized water for 1minute, and dried with an air hose.

Using an eye-dropper, a solution containing 15% by volume hydrochloricacid was applied to the roughened surface and left there for 15 seconds.On a scale of 1 to 10, where a rating of 1 indicates that the roughenedcopper surface has dissolved to reveal bare copper beneath, and where arating of 10 indicates no difference between the surface before andafter the acid test, this surface rated a 5. This demonstratesexceptional acid resistance compared to the roughened surface of Example1, which dissolved immediately upon application of the acid solution(thus rating 1 on the scale of 1 to 10). Subsequent peel strength testson a laminated portion of the roughened copper surface resulted in apeel strength value of 5.8 lbs/in.

EXAMPLES 35 THROUGH 43

For Examples 35 through 43, a roughened copper surface was prepared inthe same manner as Example 34, with the exception that the compositionand duration of the post-treatment bath was varied. Table 5 lists theparticular acid resistance promoting composition used in thepost-treatment bath in each example, along with the concentration,treatment time, peel strength test results and acid resistance testresults. The test results for each of Examples 35 through 43 demonstrateexceptional acid resistance compared to the roughened surface of Example1, which dissolved immediately upon application of the acid solution.

While the invention is described above in connection with preferred orillustrative embodiments and examples, they are not intended to beexhaustive or limiting of the invention. Rather, the invention isintended to cover all alternatives, modifications and equivalentsincluded within its spirit and scope of the invention, as defined by theappended claims.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Oxidizer 1.42wt % 1.42 wt % 1.42 wt % 1.42 wt % 1.42 wt % H₂O₂ H₂O₂ H₂O₂ H₂O₂ H₂O₂H₂O₂ 0.06 wt % 0.06 wt % 0.06 wt % 0.06 wt % 0.06 wt % stabilizer SodiumSodium Sodium Sodium Sodium Phenol- Phenol- Phenol- Phenol- Phenol-sulfonate sulfonate sulfonate sulfonate sulfonate pH adjuster 8.61 wt %8.61 wt % 8.61 wt % 8.61 wt % 8.61 wt % sulfuric acid sulfuric acidsulfuric acid sulfuric acid sulfuric acid Topography 0.57 wt % 0.57 wt %0.57 wt % 0.57 wt % 0.57 wt % modifier BTA (6 g/l) BTA (6 g/l) BTA (6g/l) BTA (6 g/l) BTA (6 g/l) Chloride ion 0.0017 wt % 0.0017 wt % 0.0017wt % 0.0017 wt % 0.0017 wt % (17 ppm) (17 ppm) (17 ppm) (17 ppm) (17ppm) NaCl NaCl NaCl NaCl NaCl Polyethylene 0.38 wt % 0.38 wt % 0.38 wt %0.38 wt % 0.38 wt % Glycol Coating None 1 ppm 5 ppm 20 ppm 100 ppmStabilizer SDDC SDDC SDDC SDDC D.I. water Balance Balance BalanceBalance Balance Acid Immediate Bare copper Bare copper Bare copper Nobare Resistance appearance visible in visible in visible in copper after(Application of of bare 10–20 20–30 50–70 3–5 minutes HCl solution)copper seconds seconds seconds

TABLE 2 Example 1 Example 12 Example 13 Example 14 Example 15 Oxidizer1.42 wt % 1.42 wt % 1.42 wt % 1.42 wt % 1.42 wt % H₂O₂ H₂O₂ H₂O₂ H₂O₂H₂O₂ H₂O₂ 0.06 wt % 0.06 wt % 0.06 wt % 0.06 wt % 0.06 wt % stabilizerSodium Sodium Sodium Sodium Sodium Phenol- Phenol- Phenol- Phenol-Phenol- sulfonate sulfonate sulfonate sulfonate sulfonate pH adjuster8.61 wt % 8.61 wt % 8.61 wt % 8.61 wt % 8.61 wt % sulfuric acid sulfuricacid sulfuric acid sulfuric acid sulfuric acid Topography 0.57 wt % 0.57wt % 0.57 wt % 0.57 wt % 0.57 wt % Modifier BTA (6 g/l) BTA (6 g/l) BTA(6 g/l) BTA (6 g/l) BTA (6 g/l) Chloride ion 0.0017 wt % 0.0017 wt %0.0017 wt % 0.0017 wt % 0.0017 wt % (17 ppm) (17 ppm) (17 ppm) (17 ppm)(17 ppm) NaCl NaCl NaCl NaCl NaCl Polyethylene 0.38 wt % 0.38 wt % 0.38wt % 0.38 wt % 0.38 wt % Glycol Coating None 1 ppm MTZ 5 ppm MTZ 20 ppm100 ppm Stabilizer MTZ MTZ D.I. water Balance Balance Balance BalanceBalance Acid Immediate Bare copper Bare copper Bare copper No bareResistance appearance visible in visible in visible in copper after(Application of of bare 10–20 40–60 70–90 3–5 minutes HCl solution)copper seconds seconds seconds

TABLE 3 Example Number Coating Stabilizer Example 16 2-mercaptobenzothiazole Example 17 2,2′-dithiobis(benzothiazole) Example 186-ethoxy-2-mercaptobenzothiazole Example 193,4,5,6-tetrahydro-2-pyrimidinethiol Example 20 2-imidazolidinethioneExample 21 potassium 3-(thiocarbamoyl)-dithiocarbazate Example 22 sodiumdimethyldithiocarbamate Example 23 tetraethylthiuram disulfide Example24 tetramethylthiuram disulfide Example 25 2,5-dithiobiurea

TABLE 4 Topography Example Number Modifier Uniformity Enhancer CoatingPromoter Example 26 5 g/l 1H-indole None None Example 27 4 g/l6-nitro-1H- None None benzotriazole Example 28 6 g/l 2-hydroxy-1H- NoneNone benzimidazole Example 29 0.57 wt % BTA 0.5 g/l 5-aminotetrazoleNone Example 30 0.57 wt % BTA None 0.5 g/l 1- hydroxybenzotriazoleExample 31 0.57 wt % 0.05 g/l 5- 2 g/l 1- tolytriazolemercaptomethyltetrazole hydroxybenzotriazole

TABLE 5 Acid Re- Post-Treatment Treatment Peel sistance Bath TimeStrength Rating* Example 1 None n/a — 1 Example 34 1 g/l disodium 15seconds 5.8 lbs/in 5 trithiocarbonate Example 35 1 g/l disodium 30seconds 5.7 lbs/in 7 trithiocarbonate Example 36 1 g/l sodium sulfide 15seconds 5.0 lbs/in 9 Example 37 1 g/l sodium sulfide 30 seconds 4.6lbs/in 9 Example 38 1 g/l sodium N,N- 30 seconds 5.5 lbs/in 5dibutyldithiocarbamate Example 39 1 g/l sodium 30 seconds 6.0 lbs/in 6dioctyldithiocarbamate Example 40 0.5 g/l HQMME- 15 seconds 6.2 lbs/in 5xanthate and 0.5 g/l Na₂ trithiocarbonate Example 41 0.5 g/l HQMME- 30seconds 6.3 lbs/in 5 xanthate and 0.5 g/l Na₂ trithiocarbonate Example42 0.5 g/l sodium N,N- 15 seconds 6.7 lbs/in 5 dibutyldithiocarbamateand 0.5 g/l Na₂ trithiocarbonate Example 43 1 g/l sodium N,N- 30 seconds6.6 lbs/in 4 dibutyldithiocarbamate *Acid resistance is rated on a scaleof 1–10, where a rating of 1 indicates that the roughened copper surfacehas dissolved to reveal bare copper beneath, and where a rating of 10indicates no difference between the surface before and after the acidtest

1. A process for preparing roughened copper surfaces suitable forsubsequent multilayer lamination, said process comprising the steps of:contacting with a copper surface an adhesion promoting composition underconditions effective to provide a roughened copper surface, saidadhesion promoting composition comprising an oxidizer, a pH adjuster,and a topography modifier; contacting said roughened copper surface withan acid resistance promoting composition selected from the groupconsisting of sodium dioctyldithiocarbamate, disodium trithiocarbonate,sodium sulfide, sodium N,N-dibutyldithiocarbamate and sodiumhydroquinone monomethyl ether xanthate; and contacting said roughenedcopper surface with a post-dip solution, said post-dip solutioncomprising an azole or silane.
 2. The process according to claim 1,wherein said post-dip solution comprises a silane selected from amongtrichlorosilanes and trimethoxysilanes.
 3. The process according toclaim 1, wherein said post-dip solution comprises a silane selected fromthe group consisting of trimethoxy-silylpropyldiethylenetriamine;3-methylacryloyloxypropyltrimethoxysilane;styrylmethyl-2aminoethylamino) propyltrimethoxysilane hydrochloride;3-(N-allyl-2-aminoethylamino)-propyltrimethoxysilane hydrochloride;N-(styrylmethyl)-3-aminopropyltrimethoxysilane hydrochloride;N-2-aminoethyl-3-aminopropyltrimethoxysilane;3-(N-Benzyl-2-aminoethylamino)-propyltri-methoxy silane hydrochloride;beta-(3,4-epoxycyclohexyl) ethyltrimethoxysilane;gamma-aminopropyl-triethoxy silane;gamma-glycidoxypropyltrimethoxysilane; and vinyltrimethoxysilane.
 4. Theprocess according to claim 1, wherein said post-dip solution furthercomprises a titanate.
 5. The process according to claim 4, wherein saidtitanate is selected from the group consisting of titanate amine;tetraocytl di(ditridecyl)phosphito titanate; tetra(2,2-diallyloxymethyl)butyl-di(ditridecyl)phosphito titanate;neopentyl(diallyl)oxytri(diocytl)pryo-phosphato titante; andneopentyl(diallyl)oxy tri(m-amino)phenyl titanate.
 6. The processaccording to claim 1, wherein said post-dip solution further comprises azirconate.
 7. The process according to claim 6, wherein said zirconateis selected from the group consisting of KZ 55-tetra (2,2diallyloxymethyl)butyl, di(ditridecyl)phosphito zirconate;NZ-01-neopentyl(diallyl)oxy, trineodecanoyl zirconate;NZ-09-neopentyl(diallyl)oxy, tri (dodecyl)benzene-sulfonyl zirconate;tetra(2,2 diallyloxymethyl)butyl-di(ditridecyl)phosphito zirconate; andzirconium IV 2,2-dimethyl 1,3-propanediol.
 8. The process according toclaim 1, wherein said post-dip solution further comprises an aluminate.9. The process according to claim 8, wherein said aluminate is selectedfrom the group consisting of diisobutyl(oleyl)acetoacetylaluminate anddiisopropyl(oleyl)acetoacetyl aluminate.
 10. The process according toclaim 1, wherein said adhesion promoting composition further comprises acopper salt.
 11. The process according to claim 10, wherein said coppersalt is copper sulfate.